1. Field of the Invention
An aspect of the present invention relates to an electron emission device, and more particularly, to a method of improving uniformity of brightness between pixels in an electron emission panel.
2. Description of the Related Art
In general, electron emission devices use hot cathodes or cold cathodes as electron emission sources.
Electron emission devices using cold cathodes as electron emission sources include a Field Emitter Array (FEA) type, a Surface Conduction Emitter (SCE) type, a Metal-Insulator-Metal (MIM) type, a Metal-Insulator-Semiconductor (MIS) type, and a Ballistic electron Surface Emitting (BSE) type.
The FEA type electron emission device uses a phenomenon in which electrons are easily emitted in a vacuum in the presence of an electric field by electron emission sources made of a material having a low work function or a high β function. Examples of FEA type electron emission devices that have been developed include an FEA type electron emission device manufactured as a sharp tip structure containing molybdenum (Mo), silicon (Si), etc., as a main ingredient, and an FEA type electron emission device manufactured using a carbon material such as graphite or Diamond-Like Carbon (DLC), or a nanomaterial such as a nanotube or a nanowire.
The SCE type electron emission device has electron emitters formed by a narrow slit in a conductive thin film between a first electrode and a second electrode opposing each other on a substrate. The SCE type electron emission device uses a phenomenon in which electrons are emitted from the narrow slits forming the electron emitters when a voltage is applied across the first and second electrodes to cause a current to flow over the surface of the conductive thin film.
In the MIM type electron emission device, electron emitters have a metal-insulator-metal (MIM) structure and electrons are accelerated and emitted while moving from a metal layer having a high voltage through an insulator layer to another metal having a low voltage when a voltage is applied between the two metal layers sandwiching the insulator.
Likewise, in the MIS type electron emission device, electron emitters have a metal-insulator-semiconductor (MIS) structure and electrons are accelerated and emitted while moving from a semiconductor layer having a high voltage through an insulator layer to a metal layer having a low voltage when a voltage is applied between the metal layer and the semiconductor layer sandwiching the insulator layer.
The BSE type electron emission device uses a phenomenon in which electrons travel without being scattered when the size of a semiconductor is reduced smaller than a mean free path of electrons. In the BSE type electron emission device, an electron supplying layer formed of a metal or a semiconductor is formed on an ohmic electrode, and an insulation layer and a metal thin film are formed on the electron supplying layer. Electrons are emitted when a voltage is supplied to the ohmic electrode and the metal thin film.
An electron emission panel formed of one of the above-described electron emission devices includes a plurality of scan electrodes extending in a first direction and a plurality of data electrodes extending in a second direction and intersecting the scan electrodes, wherein pixels are defined at intersections of the scan electrodes and the data electrodes. Each pixel emits visible light, and brightness of the pixel depends on a driving signal applied to the pixel.
Ideally, when the same driving signal is applied to different pixels of the electron emission panel, the different pixels should emit visible light having the same brightness. However, in actuality, due to the characteristics of electron emission sources of the electron emission panel and problems in a manufacturing process of the electron emission panel, visible light having different brightnesses may be emitted when the same driving signal is applied to different pixels, resulting in non-uniformity of brightness between pixels.
To solve this problem, a method of compensating for brightness differences between pixels using compensation signals generated by a compensation circuit has been proposed. However, this method has a high manufacturing cost due to the separate compensation circuit, is difficult to actually implement, and causes variations in pixel life span within an electron emission panel because different compensation signals are applied to different pixels.